The present invention relates to winding coils for lamination stacks of a stator. More particularly, the solutions of the invention are concerned with winding coils of alternator stators, and forming the relative end leads. The coils that become wound by the solutions of the invention have an undulated shape, like those that are formed by the apparatus and functioning principles described in U.S. Pat. No. 4,512,376 (herein referred to as xe2x80x9cBarrera ""376xe2x80x9d) assigned to the same assignee of this application. (Barrera ""376 is hereby incorporated by reference herein in its entirety.)
As shown in FIG. 1, which is a perspective view of a traditional undulated coil 10 formed according to the principles of Barrera ""376, coil 10 has a central axis O, which is substantially perpendicular to the various wire turns 20 of the coil, each of the wire turns defining a plane P. (Those skilled in the art will appreciate that a reference to a xe2x80x9cplanexe2x80x9d in connection with a helical coil is an approximation used for convenience herein.) Initial lead 11 of the coil is contained in lowermost plane A of the planes P, while final lead 12 is contained in uppermost plane B of the planes P. Coil 10 becomes inserted in respective slots 13 of stator stack 14 as shown in FIG. 2. This is done by means of an insertion operation requiring pushing of the coil in the longitudinal direction 15, parallel to axis O with the stator stack in an overhead position, aligned with axis O. The coil is placed on an insertion tool (not shown) to accomplish such an operation. In pushing the coil into the stator stack, radial arms 16 of the coil become inserted in the slots 13, while bridging sections 17 form the end portions of the coils, and are located outside the extreme faces of the stack. As shown in FIG. 2, leads 11 and 12 have been rotated to become practically parallel to axis O. In FIG. 2 the stator stack has been turned upside down with respect to the position which it would have when pushing in direction 15 of FIG. 1 during the insertion operation. The distances of leads 11 and 12 from axis O after the coil has been inserted in the stator stack are particularly pertinent to presentation of this invention. As shown in FIG. 2, initial lead 11 is nearer to axis O than final lead 12.
Usually, at least three coils (often referred to as phase coils) like coil 10 are inserted in the stator stack to form the final product. These can be inserted into the stator stack simultaneously or separately. Each coil will be inserted in respective and different sets of slots. When inserted, the coils will be at different radial distances from center axis O of the stack, as shown by references R1, R2 and R3 in FIG. 3, corresponding to coils 8, 9, and 10. FIG. 3 is a partial view of the stator, as seen from direction 3xe2x80x943 of FIG. 2, but with all three coils inserted, as would be required in the final product. For sake of clarity only one coil has been shown in FIG. 2.
It is clear from FIG. 3 that initial lead 11 of coil 10 (the nearest to axis O) can be very near to central opening 10xe2x80x2 of the stack. This is also evident from FIG. 3a, which is a view from direction 3axe2x80x943a of FIG. 3. (The location of axis O is not shown accurately in FIG. 3a or FIG. 11 to avoid unduly enlarging these FIGS.) Furthermore, initial lead 11 does not have bridge portions 17 between itself and central opening 10xe2x80x2. This renders initial lead 11 more unstable to lateral displacements (in particular, in the radial direction with respect to the central axis) compared to the other leads. Because of this, small accidental displacements of initial lead 11 toward center axis O can cause it to enter central opening 10xe2x80x2 of the stator stack. Such a situation can cause a physical interference of the initial lead 11 with the rotor that is destined to rotate in central opening 10xe2x80x2. A frequent consequence of this is damage to the initial lead.
In view of the foregoing, it would be desirable to provide improved methods and apparatus for winding undulated coils for dynamo-electric machine stators. It would also be desirable to provide methods and apparatus for winding undulated coils for dynamo-electric machine stators that reduce the likelihood of damage to lead wires. It would further be desirable to provide an undulated coil whose wire leads are less susceptible to damage.
It is an object of this invention to provide improved methods and apparatus for winding undulated coils for dynamo-electric machine stators. It is also an object of this invention to provide methods and apparatus for winding undulated coils for dynamo-electric machine stators that reduce the likelihood of interference between lead wires and rotors of dynamo-electric machines. It is a further object of this invention to provide an undulated coil whose wire leads are less susceptible to damage.
These and other objects are accomplished by providing a wire coil winding head which includes, among other features, a gripper configured to hold an initial lead of the wire; a receiver structure configured to receive the wire extending from the gripper and to form a coil of the wire having successive turns that are substantially disposed in respective planes that are substantially perpendicular to a central longitudinal axis of the coil and laterally spaced from one another along that axis; a forming structure configured to produce undulations in the turns of wire in their respective planes while the turns are on the receiver structure, the undulations giving the turns portions that are substantially radial of the axis; and a gripper positioning structure configured to position the gripper relative to the receiver structure so that the initial and final leads can be placed substantially in the same plane as each other and each lead can also be substantially aligned with a respective portion of the coil that is substantially radially disposed with respect to the longitudinal axis. Accordingly, the invention permits both initial and final leads, as installed in a stator, to be disposed at a safe distance from the rotor destined to rotate within the stator.